The present invention relates to a method of correcting a learning capacity of a battery, which becomes a reference in calculation of a residual capacity of a battery, in a charging and discharging cycle and or an inactive state. In the present specification, the learning capacity means a corrected full charge capacity of a battery.
A battery is slightly degraded in keeping, and a full charge capacity is gradually decreased. In the case where a residual capacity of a battery is expressed as a relative value to the full charge capacity by, for example, %, it is important to accurately correct the full charge capacity (FCC). As a correction method of the full charge capacity, various methods have been proposed. For example, charge capacity until a completely discharged battery is fully charged is integrated to calculate the full charge capacity, alternatively discharge capacity until the fully charged battery is completely discharged is integrated to calculate the full charge capacity, the calculated full charge capacity is made a correct value, and the former full charge capacity is corrected. This method can accurately correct the full charge capacity of the battery.
However, in the method of calculating the full charge capacity in the state in which the completely discharged battery is fully charged or the fully charged battery is completely discharged, the timing when the full charge capacity is calculated and can be corrected becomes an extremely limited state. Thus, the frequency of correcting the full charge capacity is low and an error becomes large between corrections. For example, if a battery is maintained in a state where charging and discharging are not performed in a long period of, for example, several months or one year, the fully charged or completely discharged state does not occur, and the full charge capacity can not be accurately corrected. Thus, when the battery is used after storing for a long period, an error of an indication of the residual capacity becomes large.
Further, even in the case where the battery is used in a state where charging and discharging are performed, in the method in which the charge capacity or the discharge capacity between the full charge and the complete discharge is calculated and a correction is made, if the battery is used in the state where it is not completely discharged, it is impossible to calculate and correct the full charge capacity. In the case where the battery is used as a power source of an electrical equipment such as a laptop microcomputer, the battery is held in the fully charged state in almost all cases. This is because the electrical equipment is always put in a usable state so that it can be conveniently used. When the battery is completely discharged, the electrical equipment using this as the power source can not be used. Before this electrical equipment is used, it is necessary to charge the battery over a long period of time. In this use state, the electrical equipment can not be conveniently used. Thus, although the method of calculating and correcting the full charge capacity between the full charge and the complete discharge has the feature that the full charge capacity can be accurately corrected, it has a defect that the full charge capacity of the battery can not be always accurately corrected.
The present invention has been developed in order to solve this defect. A primary object of the present invention is to provide a residual capacity correction method for a battery in which a learning capacity as a full charge capacity of the battery can be corrected simply, easily and more accurately.